In recent years, progress has been made in networking home appliances, mainly audio-video equipment. Thereby, the home appliances can interact with each other by detecting other home appliances through networks (home networks). More specifically, when a call is made through an intercom installed at, for example, an entrance, information indicating occurrence of the call and video captured by a camera included in the intercom are displayed on a television and others.
Such an interactive operation needs a mechanism for notifying other home appliances (hereinafter each referred to as event receiving apparatus), such as a television, of a state change (event) occurring in a home appliance (hereinafter referred to as event transmitting apparatus), such as an intercom. The Universal Plug and Play (UPnP) Device Architecture is known as the industry standard specification for providing the mechanism for the event notification (for example, see Non-patent Reference 1).
However, although the UPnP provides the mechanism for the event notification, the specification relies on each apparatus to uniquely define details of each event. Thus, there is a problem that the event receiving apparatus needs to know the definition and the processing method of each event so that the event receiving apparatus performs processing corresponding to the received event.
Accordingly, the event receiving apparatus needs to incorporate the processing method suitable for the event transmitting apparatus in advance. Thus, the event receiving apparatus has a difficulty of later adding an event transmitting apparatus as an apparatus to interact with.
As a method for solving the problem, what is known is a method including: placing, in a web page, information items (or user interfaces for processing) to be provided in association with respective events; and transmitting a Uniform Resource Locator (URL) included in a parameter in an event message when an event is notified so that the event transmitting apparatus accesses the web page (for example, see Patent Reference 1).    Non-patent Reference 1: UPnP Device Architecture 1.0    Patent Reference 1: Japanese Unexamined Patent Application Publication No. 2006-260125